The long term objective of these studies is to develop genetically defined systems for targeting gene expression to the prostate of transgenic mice based on regulatory elements of genes, viral or cellular in origin, that previously have been shown to be expressed in the various cell-types of the prostate. Since a major focus of the SPORE Molecular Mechanisms Group (SMMG) is to initiate perturbation analysis experiments to facilitate direct characterization of the molecular and cellular mechanisms governing transformation of the differentiating prostate in vivo, the studies in this proposal will provide SPORE investigators with vectors to direct aberrant oncogene- or tumor suppressor gene expression to the prostate in transgenic mice. The rationale for developing vectors exhibiting unique prostate- specific patterns of temporal and spatial expression and hormonal regulation is that the timing and level of targeted gene expression in the appropriate mesenchymal and epithelial cell types may influence the progression of prostatic disease. Initial studies will evaluate the efficacy of genomic fragments derived from the 5' flanking regions of the rat probasin (PB), seminal vesicle secretory II protein (SVSII) and human prostate specific antigen (PSA) genes, respectively, to direct prostate- specific expression of the bacterial chloramphenicol acetyltransferase (CAT) reporter gene in six week old transgenic mice. Depending on the outcome of these experiments, transgenic mice will be generated with constructs bearing the PB, SVSII or PSA promoters fused to a modified bacterial beta-galactosidase gene, pnlacF, to more carefully characterize the temporal, spatial and hormonal regulation of transgene expression. Parallel studies will place pnlacF under the transcriptional control of a minimal promoter fused to "upstream activation sequences" (UAS; =GAL4 binding sites) to generate "responder" lines of mice that will subsequently be mated with separate transactivator mice harboring a MMTV-LTR-GAL4 transgene. The temporal and spatial expression patterns of the activated pnlacF transgene will be characterized in the "bigenic" offspring. Since transgenes normally remain quiescent in responder lines, the bigenic system overcomes breeding problems associated with male sterility that may occur as a consequence of activated transgene expression in the prostate. Hence, PB-, SVSII- and PSA-driven bigenic systems will also be developed. therefore, this project will facilitate the establishment of suitable animal models that will be used to identify biological factors involved in the progression of prostate cancer with the longterm goal of using these models for the development and testing of medical therapies for the prevention of such progression in collaboration with other SPORE investigators.